Dresden 2014 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 32: Poster: ZnO and its relatives

HL 32.4: Poster

Monday, March 31, 2014, 17:00–20:00, P2

Terahertz spectroscopy on electron transport in disordered zinc oxide — •Stefan Gerhard Engelbrecht, Ludovica De Angelis, Marc Tönnies, and Roland Kersting — Photonics and Optoelectronic Group, Physics Department and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Germany

The characterization of disordered semiconductors by conventional electronic techniques is challenging since slow processes such as hopping transport or scattering at grain boundaries mask the fast transport within the crystallites. Terahertz (THz) time-domain spectroscopy offers an alternative approach for characterizing charge transport in disordered semiconductors. We report on THz spectroscopy of electron transport in nanocrystalline zinc oxide deposited by spray pyrolysis. In our experiments, the electromodulation of charge carriers in the ZnO films leads to a differential THz signal, which provides the AC conductivity. The experiments reveal an unexpected deviation from Drude transport that exhibits a negative imaginary conductivity over the accessible frequency range. Both, the Drude-Smith model as well as the Bruggeman model reproduce the experimental data well. The analysis delivers the fundamental scattering times and reveals the percolated nature of high frequency conductivity in disordered films.